Remove ENABLE_CUSTOM_ELEMENTS compile time flag

Source/core/page/RuntimeEnabledFeatures.h

Index: Source/core/page/RuntimeEnabledFeatures.h
diff --git a/Source/core/page/RuntimeEnabledFeatures.h b/Source/core/page/RuntimeEnabledFeatures.h
index fd458ef4582a45db49c34e18a4adca75e5f70c80..10c4c2be8ec037430d52e2cf484e8300eb6838f2 100644
--- a/Source/core/page/RuntimeEnabledFeatures.h
+++ b/Source/core/page/RuntimeEnabledFeatures.h
@@ -199,10 +199,8 @@ public:
     static bool authorShadowDOMForAnyElementEnabled() { return isAuthorShadowDOMForAnyElementEnabled; }
     static void setAuthorShadowDOMForAnyElementEnabled(bool isEnabled) { isAuthorShadowDOMForAnyElementEnabled = isEnabled; }
 
-#if ENABLE(CUSTOM_ELEMENTS)
     static bool customDOMElementsEnabled() { return isCustomDOMElementsEnabled; }
     static void setCustomDOMElements(bool isEnabled) { isCustomDOMElementsEnabled = isEnabled; }
-#endif
 
     static bool styleScopedEnabled() { return isStyleScopedEnabled; }
     static void setStyleScopedEnabled(bool isEnabled) { isStyleScopedEnabled = isEnabled; }
@@ -298,9 +296,7 @@ private:
 
     static bool isAuthorShadowDOMForAnyElementEnabled;
 
-#if ENABLE(CUSTOM_ELEMENTS)
     static bool isCustomDOMElementsEnabled;
-#endif
 
     static bool isStyleScopedEnabled;